The present invention relates to a metal-made seamless pipe and a process for producing such a pipe. More particularly, the present invention relates to a metal-made seamless pipe which is low in processability but can be produced having a small thickness and a small inner diameter, having superior mechanical strength and gastightness, and which can be suitably used, as a sealing member of a translucent vessel (e.g. a ceramic-made translucent vessel) of, for example, a high-pressure discharge lamp (e.g. a metal halide lamp). The present invention also relates to a process for producing such a metal-made seamless pipe.
As shown in FIG. 5, a translucent ceramic pipe 20 (a translucent pipe) is used as a translucent vessel of a high-pressure discharge lamp 10 (e.g. a metal halide lamp), because the translucent vessel contains a light emitting material (e.g. dysprosium iodide) of high corrosivity and accordingly requires corrosion resistance.
In order to seal the translucent ceramic pipe 20 (a translucent pipe) used as a translucent vessel, a metal-made pipe 30 (e.g. a Mo pipe) was proposed as a sealing member (European Patent Publication EP 0982278A1).
The metal (e.g. Mo or W) used in such a metal-made pipe, however, is generally low in processability and there has been a limit in producing the pipe in a small thickness and a small inner diameter.
Since the metal is low in processability and its cutting is difficult, production of a metal-made pipe therefrom has ordinarily been conducted by sintering a metal ingot and subjecting the sintered metal ingot to rolling, drawing or the like to obtain a pipe-shaped material. In such a production process, it has been extremely difficult to obtain a metal-made pipe of small thickness and small diameter.
In view of the above-mentioned problems, the object of the present invention is to provide a metal-made seamless pipe which is low in processability but can be produced having a small thickness and a small inner diameter, having superior mechanical strength and gastightness, and which can be suitably used as a sealing member of a translucent vessel (e.g. a ceramic-made translucent vessel) of, for example, a high-pressure discharge lamp (e.g. a metal halide lamp), and a process for producing such a metal-made seamless pipe.